Mode of File

A file can be opened in variuos modes dependent on whether it is to be opened
for reading or writing or both. We here define a set that is largely equivalent
to what we know from ANSI C file modes and Unix file modes:

Open a Local File

Opens a local file using whatever means are available on the current platform.
If we have unix file descriptors then use that as we can use select on them.
On windows we want to use asynchrounous handles - just like we handle the
socket interface as well. On other platforms, we use ANSI C file descriptors.

extern int HTFileOpen (HTNet * net, char * local, HTLocalMode mode);

Close a Local File

Closes a file descriptor whatever means are available on the current platform.
If we have unix file descriptors then use this otherwise use the ANSI C file
descriptors